1. Field of the Invention
The present invention relates to a vibration-reduction mechanism for a gear cutting machine that performs gear cutting on a gear blank with a rotary tool attached to a main shaft made to move reciprocally by a crank mechanism.
2. Description of the Related Art
Gear cutting machines, such as gear shapers, are provided as conventional machines to perform gear cutting on a gear blank with a rotary tool. When a gear cutting machine of this type is used, a workpiece (gear blank) is formed into a desired gear shape by making a rotary cutter (rotary tool) and the rotating workpiece mesh with each other and then making the cutter move reciprocally in the axial direction of the workpiece.
The reciprocating motion of the cutter is achieved by making a main shaft to which the cutter is attached move in its axial direction by moving a crank of a crank mechanism. Such reciprocating motion of the main shaft, however, produces vibrations in the machine due to the inertial force of the main shaft and the like. The vibrations may possibly affect negatively the machining accuracy. Accordingly, as a countermeasure for such vibrations in conventional gear cutting machines, a balancer weight is provided on the outer perimeter of a crank shaft of the crank mechanism (see, Patent Document 1).
The conventional gear cutting machines are capable of changing the stroke width of the reciprocating motion of the cutter so as to deal with workpieces of various face widths. The changing of the stroke width is naturally accompanied by the changing of the magnitude of the vibrations caused by the reciprocating motion of the main shaft. Accordingly, various gear cutting machines are provided with vibration-reduction mechanisms to adjust easily the weight of the balancer weight in accordance with the stroke width (see Patent Documents 2 to 4).    [Patent Document 1] Japanese Utility Model Application Laid-open Publication No. Sho 60-45640    [Patent Document 2] Japanese Examined Utility Model Publication No. Sho 58-35386    [Patent Document 3] Japanese Utility Model Application Laid-open Publication No. Sho 61-97643    [Patent Document 4] Japanese Utility Model Application Laid-open Publication No. Sho 61-97644